No Defroster

I got in my blazer the other day and noticed my defroster was not working, when I turn on the defroster it blows out the vents but not up under the windsheild. Anyone know what the problem would be. Thanks

Check to make sure that all your vacuum lines are hooked up and have no leaks. Your AC controler switch on your dashboard uses vacuum to move the baffles in your ducts from defroster, vents, and heater.